This invention relates to a fault detector for an electrical transmission system and a remote current sensor for use therein. The remote current sensor measures the magnetic field surrounding a conductor of the transmission system to monitor the current flowing through the conductor. The remote current sensor is positioned at a location sufficiently distant from the conductor to prevent electrical arcing from occurring without the use of an insulating material. The fault detector responds to the output of the remote current sensor to detect a fault within one quarter of the fault current cycle.
Fault detectors have been known in which a current transformer is used to monitor the current flowing through a conductor of an electrical transmission system. A current transformer typically requires an expensive insulating material such as porcelain to protect the transformer from electric fields. Fault detectors have also used a Hall effect transducer to monitor the current flowing through a conductor but alone the transducer is ineffective at distances from the conductor greater than the electrical arcing distance. At distances sufficiently close to the conductor to provide a meaningful measurement, the Hall effect transducer requires the same insulation as the current transformer to protect the transducer from electric fields.
Known fault detectors further require a full half-cycle of fault current to respond thereto. During the time required to detect a fault, costly equipment may be damaged. Additional problems arise in locating the fault after it has been cleared by the transmission system's interrupting devices.